Looks like a broken or overheated gfx card to me mate.
Okay, so the card. I wonder if it's this I found:
"In addition, motherboards with some VIA and SIS chipsets and an AMD Athlon XP processor seemingly have compatibility problems with the GeForce 6600 and 6800 GPUs. Problems that have been known to arise are freezing, artifacts, reboots, and other issues that make gaming and use of 3D applications almost impossible. These problems seem to happen only on Direct3D based applications and do not affect OpenGL.[2]"
the processer is an AMD Athlon 64 X2 5000+ socket AM2
I dunnoif that's an Athlon XP, but it does seem quite close. (?)
If it's just the card, I was planning on getting her a better card eventually anyways. (I noticed the 9500GT is quite a bargain or seems so.)
When I get her off her PC, I'll try the onboard graphics and see what happens....